The invention relates generally to the field of electrical power transmission networks and in particular to a technique for synchronized phasor measurement based on multi-parameter model of the fundamental frequency component of the signal.
The application of synchronized phasor measurements of voltages and currents from widely dispersed locations in an electrical power transmission network is well recognized for monitoring, operation and control of the power system network. Traditionally, power systems may be monitored through a combination of non-synchronized measurements, power flows and voltage magnitudes, feeding into a software model of the network which using other parameters of the network, calculates the balance of quantities. These quantities may however be calculated directly using synchronized phasor measurements (that is, phasor measurements with reference to absolute time). The phasor measurement unit (PMU) is considered to be one of the important measuring devices in the future of power systems because of its ability to provide synchronized phasor measurements. There are a variety of methods and many possible hardware implementations for providing synchronized phasor measurements.
However, the current techniques and phasor measurement units provide synchronized phasor measurements with desirable accuracy only in the steady state condition. During transient conditions, especially during power swings or during transient changes in power system frequency, both magnitude and phase angle change. Thus, Fourier-like algorithms derived from signal models that assume amplitude, frequency and phase angle to be constant for computing synchronized phase measurements, provide erroneous results as the assumptions are violated during transient conditions. Changes in amplitude, frequency, or phase angle generate cross coupling errors. For example, a change in phase angle creates an error in estimated magnitude, and a change in magnitude creates an error in estimated phase angles. Hence, present methods for computing synchronized phase measurements have limitations for achieving high levels of accuracy during the transient conditions.
It is therefore desirable to provide a signal model and a technique for synchronized phasor measurement based on the proposed signal model that would yield better accuracy under realistic system conditions, particularly during transient conditions.